Speaker: Nicole Larsen, Kalvi Institute for Cosmological Physics, Univ Chicago
Abstract: The Large Underground Xenon (LUX) dark matter search is a 370-kg dual-phase xenon-based time projection chamber that operates by detecting light and ionization signals from particles incident upon a xenon target. With its 2013 report of the world’s first sub-zeptobarn spin-independent WIMP-nucleon cross section limit, LUX emerged as a frontrunner in the field of dark matter direct detection. In December 2015, LUX released an updated analysis of its 2013 dataset leading to an overall 23% increase in sensitivity for high-mass WIMPs and even more significant improvement for low-mass WIMPs. And in July 2016, LUX released results from an extended 332-day dataset, finding no evidence of WIMPs and improving its limit to a minimum of 0.2 zeptobarns for 50-GeV WIMPs. However, tension between experiments and the absence of a definitive positive detection suggest it would be prudent to search for WIMPs outside the standard spin-independent/spin-dependent analyses. Recent effective field theory work has identified a complete set of 14 possible independent WIMP-nucleon interaction operators restricted only by basic symmetries. These operators produce not only spin-independent and spin-dependent nuclear responses but also novel nuclear responses such as angular-momentum-dependent and spin-orbit couplings. Here we report on the extension of the LUX analysis to search for all 14 of these interactions, comment on the possible suppression of event rates due to operator interference, and investigate several other prominent direct detection experiments to show that under this new framework, LUX again exhibits world-leading sensitivity.